Pressure actuated switch



Jan. 1, 1946.

A. T. NEWELL PRESSURE vACTL IATED SWITCH Filed May 25, 1943 2 Sheets-Sheet l m E. s A

INVENTOR Apr/aw? 272-14221- BY Jan. 1, 1946. 1 NEWELL 2,391,916

PRES SURE ACTUATED SWITCH Filed May 25, 1943 2 Sheets-Sheet 2 INVENTOR. Iirfldfi 7742/1 54:

Patented Jan. 1, 1946 PRESSURE ACTUATED SWITCH Arthur T. Newell, Huntington, N. Y., assignor to Kenyon Instrument 00., Inc., Huntington Station, N. Y., a corporation of New York Application May 25, 1943, Serial No. 488,360

6 Claims.

This invention relates to pressure actuated switch mechanism and more particularly to an air speed switch for airplanes.

An object of the invention is to provide a switch of the above type having novel and improved details of construction and features of operation.

In accordance with the present invention a balanced bellows mechanism is provided for operating the switch contact arm through a linkage providing a limited amount of lost motion so that the contact, when closed, remains closed over a predetermined range of movement of the bellows, thereby preventing unstable operation.

Another feature of the invention consists in providing internal plug members for reducing the available volume of the bellows so as to increase the sensitivity thereof to changes in air pressure in the supply tubes. The plug members also act as built-in stops to limit the compressional movement of the bellows.

Another feature consists in the provision of capillary metering orifices in the supply tubes which serve to dampen the operation of the device and to eliminate variations in operations which might otherwise occur if the tube area should change, as by the partial closing or the partial plugging of a tube.

The invention also provides novel and improved contact mechanism for successively closing a plurality of different contacts as the air speed changes, with a snap action at each make or break. The contacts are so arranged that the contact periods and the gap periods may be varied over a wide range by a simple adjustment. The contacts are also arranged to be self-cleaning.

Although the novel features which are believed to be characteristic of this invention are pointed out more particularly in the claims appended hereto, the invention itself may be better understood by referring to the following description, taken in connection with the accompanying drawings in which a specific embodiment thereof has been set forth for purposes of illustration.

In the drawings,

Fig. 1 is a vertical section through a switch mechanism embodying the present invention;

Fig. 2 is a transverse vertical section taken on the line 2-2 of Fig. 1;

Fig. 3 is a diagrammatic view of the switch mechanism connected by static and Pitot lines to an airplane wing;

Fig. 4 is a detail view of a switch plate illustrating another embodiment of the invention;

Fig. 5 is a transverse section taken on the line 5-5 of Fig. 4;'

Figs. 6 and 7 are detail views of switch plates illustrating further embodiments of the invention;

Fig. 8 is a detail view of a switch plate and contact arm illustrating a still further embodiment of the invention; and

Fig. 9 is a transverse section taken on the line 9-9 of Fig. 8.

In the following description certain specific terms are used for convenience in referring to various details of the invention. It is to be understood, however, that these terms are to be given as broad an interpretation as the state of the art will permit.

Referring first to Figs. 1 and 2, the switch is shown as comprising a base plate Ill having a suitable cover I l secured thereto by means shown as screws 12. The base plate 10 carries a pin 14, the outer end of which is supported by a stationary bracket I5 attached to the base plate It] by screws [6. v

A segmental contact plate 20 and a sleeve 2l are pivotally mounted about the pin I l. The contact plate 20 is adjustably secured to the base plate In by suitable means shown as screws 22, which extend through elongated arcuate slots 23 in the contact plate.

In the embodiment of Figs. 1 and 2 the contact plate carries a plurality of contact segments 24 to 26 which are positioned to be successively engaged by a moving contact 21 as the latter sweeps across the contact plate 20.

The contact 2'! is carried by a fiat spring member 30 which is biased to hold the contact 21 in firm engagement with the contact segments 24 to 26. The member 30 is attached by a sleeve 31 and a set screw 32 to a spring arm 33 which is attached by a collar 34 and a set screw 35 to the sleeve 2| for turning therewith. The spring arm 33 is adapted to flex in response to the turning movement of the sleeve 2| so as to build up a force for overcoming the resistance of the contact 21. I

In the embodiment shown in Figs. 1 and 2 the contact segments 24 and 26 are positioned at opposite sides of the contact plate 20 with the contact segment 25 in an intermediate position. The inside edges of the contact segments 24 and 26 are provided with grooves 24a and 26a and the side edges of the segment 25 are provided with grooves 25a which are similar to the grooves shown in section in Fig. 5 and are adapted to receive and temporarily restrain the contact 21 as trailing recess 25a; The snap action above described in connection with the recess 24a is then repeated, the contact 21 finally snapping out of the trailing recess 25a onto the insulating surface of the contact plate between the segments and '26. This action is repeated as the contactreaches the plate 26.

During the above operation the spring member serves to hold the contact 2'! in engagement with the various contact segments. The ratio of gap period to contact period may be controlled by adjusting the position of the sleeve 3| on the spring arm 33 so as to thereby vary the radial position of the contact 21. In the embodiment shown in Fig. l, the contacts 24, 25 and 26 taper toward the axis of the pin I4 but have a greater angular width as the axis is approached. The gaps between the contact segments 24, 25 and 26 have a correspondingly less angular width as the axis is approached. Hence, as the contact 21 is shifted toward the axis, the ratio of the contact area to the gap area is increased. In this way any desired ratio may be obtained by suitable adjustment of the position of the sleeve 3| along the spring arm 33.

The setting of the contacts may be further adjusted by shifting the angular position of the contact plate 20 about the pin I4 within the limits of the elongated slots 23. The plate 20 may be secured in adjusted position by the screws 22.

It is of course to .be understood that an additional number of contact segments may be provided if further circuit connections are required. Figs. 4, 6 and '7 illustrate different embodiments of the invention wherein the contact segments are differently arranged. In Fig. 4 the contact plate I00 tapers away from the axis. This permits a greater range in adjustment of the ratio of contact area to gap area, It is to be understood, of course, that a plurality of such contact segments I00 may be provided if desired.

In Fig. 6 the contact segment I02 is provided with parallel side edges. This provides for a range of adjustment which is intermediate between that obtained by the embodiments of Figs. 1 and 4.

Fig. '7 shows the application of the invention to an embodiment wherein only a single make and break contact is required. Such embodiment may be used, for example, when it is desired to close .the contact when the plane speed falls to a predetermined minimum value, such, for example, as a value at which it is desired to lower the wing flaps. These flaps may thus be automatically lowered when the plane speed falls to the predetermined value without further attention on the part of the pilot. A single contact, as shown in Figs.

i 4 and 6, may be used, for example, to indicate normal flying speed and to open the circuits when the flying speed varies either above or below its normal value. The embodiment shown in Fig. 1 may be employed, for example, to lower the wing flaps when the contact 24 is closed, to raise the same when the speed becomes sufiicient to open the contact 24, to close the contact 25 for a visual indication of normal flying speed when the latter is reached, and to close the contact 26 for an indication of excessive speed. Various other arrangements will be obvious to a person skilled in the art.

Referring now to Figs. 8 and 9, the pin I4 and the control mechanism is similar to that described above.- The contact plate 20 of Fig. 8, however, carries a pair of upstanding contacts I20 which are slidably mounted on brackets I2 I.

trolling the sleeve 2I is similar to that above described.

In this embodiment, the contact I25 is caused to selectively close one of the contacts I20 as the air speed varies above or below a predetermined medium value. It is to be noted, however, that after the contact |20 has been closed it remains closed regardless of further movement of the bellows and further turning movement of the sleeve 2 I, the arm I24 flexing as indicated in dash lines for this purpose. However, as the arm I24 flexes, the contact I25 is caused to wipe across th surface of the contact I20,thereby cleaning the same and insuring a good contact.

Although certain specific embodiments of the invention have been shown for purposes of illus-. tration, it is to be understood that various changes and modifications may be made therein and that the invention may be applied to various uses as will be readily apparent to a person skilled in the art. The invention is only to be limited in accord-.

ance with the scope of the following claims.

What is claimed is:

1. A pressure responsive instrument comprising an expansible bellows having rigid end members and collapsible sides forming a closed internal pressure chamber, an external member connected to be actuated by expansion and contraction of said bellows, and an internal plug in said bellows extending substantially the entire axial length thereof to form a stop to limit .the compressional movement of said bellows, said plug having a sectional area suited to substantially fill the fluid space in said bellows for thereby reducing the fluid content without reducing the effective length of the bellows.

2. A pressure responsive instrument comprising an expansible bellows having rigid end members and collapsible sides forming a closed internal .pressure chamber, an external member connected to be actuated by expansion and contraction of said bellows, and an internal plug in said bellows extending substantially the entire axial length thereof to form a stop to limit the compressional movement of said bellows, said plug having a sectional area suited to substantially flll the fluid space in said bellows for thereby reducing the fluid content without reducing the effective length of the bellows, and a supply duct extending through said plug to communicate with the interior of said bellows, and a coupling member for coupling said duct to an external tube, said coupling member including a capillary tube within said duct forming a metering orifice to dampen th action of said bellows.

3. A pressure responsive instrument comprising a pair of expansible bellows, each having a rigid base, collapsible sides and movable end diaphragms, a support carrying said rigid bases with the respective bellows in axial alignment and with their movable end diaphragms adjacent but spaced apart, aligned recesses in said diaphragms, a link extending between said diaphragms and having members seated in said recesses, said link holding both of said bellows under compression and being removably secured by the compression of said bellows and a member connected to be actuated by said link.

4. In a pressure actuated switch, an expan- The brackets I2I ar adjustably secured to the able contact butto release the samevtith vsnan action for opening said contacts in resp nse to increased pressure. built up by flexing. of said springaarm due to Expansion or contraction of said bellows;

' 5.. :Inapressure actuated switcli, an expansible bellows mechanism responsive: to. pressure changes, a base carryingsaidabellows, a'fixedcontact. member mounted :onsaidbase; a swing arm pivotedsito ,said base; coupling". means connecting said arm to be actuated by expansionjor c.ontra.c= tionof said bellows, a movable contactcarried by said .arm to sweep across'saidcontact member, said" contact member being segmental inshape and tapering radially in: angular widthwitha depression to receive said imovable..contacti extendingzialong at. least one. radial edge, said .de-'

pression having an: edge slope 1 suited to restrain aid nota le contac ut rel ase the witlia scan action in: espo se r ere se res:

u e builtun hr flex n o s rmine sai c ntac s and means ad ust v adial. nositi n isaid morable on .ct alo said armtova y the an ular q 6. In a pressure actuated switch; eigpansiblebel ows mech nism responsive to;- pres u chan es. a base carryin sa d el ows, a nin;carr-. ricd'br sa d base, a con act p ate and a; spring contact arm eachpiVQted for movement about said pin, coupling means connecting; said :arm to be actuated by. expansion or contraction. of

said loellows, amovable contact carried jbysaid' arm, a. plurality of segmental contact members carried by'said plate to be: successively engaged bysaid movable contact, said members tapering radially in angular width and having depres'r. sions: extending along their radial edges to re? ceive saidmovable contact with .a snap action for closing said contacts, said depressions having edge slopes suited to-restrain:saidmovable contact but to release the same with a snap action for opening said contacts in response to increased pressure built up by flexing of said spring arm, means angularlyadjusting said contact plate about said pin, and means adjusting the radial position of said movable contact along said arm to vary-the angular arcs'of contact. I

ARTHUR 'I 

